Gases such as oxygen, nitrogen and argon have widespread use throughout industry and medicine. Manufacturing companies and hospitals commonly purchase their needs of gases from gas distributors that take liquified oxygen, nitrogen, argon, etc. from large storage tanks and deliver them as gases to smaller tanks which are usually cylindrically shaped and, therefore, are commonly referred to as "cylinders." The distributors usually own the tanks and send the tanks filled with compressed gases to their customers. When the tanks are spent, they are returned to the gas distributor who refills them with compressed gas.
For many years, the process of filling the cylinders was performed manually. The gas distributor would have a large storage tank filled with liquified oxygen, for example. Via a manifold, he would simultaneously fill ten, twenty or more tanks. As a first step, the tanks were vented, meaning that what was in the tanks was bled off. Usually a pumping system was connected to the manifold to draw a vacuum to evacuate the tanks. Often one or more purges was performed, meaning the tanks would be filled with some of the compressed gas which was then vented. Then, the tanks were again evacuated. This purging cycle could be repeated as many times as was necessary to achieve the desired purity of the tanks. Finally, the tanks were filled to the specified pressure at a stated temperature. In performing these various steps, the operator would monitor the temperature of the tanks and the pressures in the system. For example, when the tanks were vented, the operator would monitor the pressure in the tanks and when it reached a predetermined level, he would know it was time to start the evacuation process. Again, he would monitor the pressure to determine when the next step would be taken. The entire process was very time consuming and resulted in much lost time for the operator and the equipment. Also, the pumps, which were expensive, were used only a small fraction of the day.
It has been recognized that computer control of the filling process would substantially reduce the time it would take to vent, evacuate and fill tanks, and thereby increase the number of a tanks that an operator could fill during a given time period. There are computerized systems in the marketplace. They are usually made for a particular system to fill tanks with a particular gas. Such a system often incorporates one or more manifolds, a fill pump for each manifold and a vacuum pump for each manifold. With this type of system, one group of tanks is filled with one gas, such as oxygen, through one manifold, and the other manifold is used to fill the tanks connected thereto with a different gas, such as nitrogen. Another system may also include two manifolds, but a single vacuum pump and a single fill pump to enable two groups of tanks to be filled with the same gas. A gas distributor tells the manufacturer of the controller which of these configurations he plans to utilize and then the manufacturer programs the computer to match the configuration. Other information is added to the computer program by the manufacturer, such as details on the performance characteristics of the pressure and temperature transducers, the electronically controllable valves, etc.
Thus, the manufacturer of currently available controllers makes each controller to the order of its customer, each with a particular computer program.
If the gas distributor's needs change and he wants to use both manifolds for the same gas, for example, or has to purchase a different pressure transducer because the original one is no longer operable, currently available controllers would have to be reprogrammed by the manufacturer.
Gases used for medical purposes, such as those used in hospitals, are considered drugs and, therefore, are regulated by the FDA. The FDA specifies steps to be performed to achieve a certain level of purity and to check the integrity of these tanks before they are filled. Reports must comply with certain FDA regulations.
Presently available, computerized systems do not provide automatic purging, where purging is desired, for a selected number of purging cycles.
Also, these prior-art systems accommodate a single pressure when the tanks are connected to a single manifold. The tanks are pressure rated at a particular temperature (usually 70.degree. F.) stamped on the cylinder. There are a number of common tank pressure ratings. It is not uncommon for a gas distributor to have a huge inventory of these tanks, numbering in the thousands, having a variety of pressure specifications. Presently available controllers require that only tanks having the same pressure specification be connected to the manifold so that they can all be filled to that pressure. As a result, the distributor may not have enough tanks of a certain pressure specification to be connected to all of the ports of the manifold and those ports go unused.